1. Field of the Invention
The present invention relates to an optical disc apparatus for recording and/or reproducing data on an optical disc such as a CD (compact disc) or a DVD (digital versatile disc).
2. Description of the Related Art
In the optical disc apparatus, data are reproduced from the optical disc such as the CD or DVD, and the data are recorded on recordable optical disc such as a CD-R, CD-RW, DVD-R, DVD-RW, or the like by an optical head called “optical pickup”. Data recording tracks are formed concentrically or spirally on such the optical disc. The optical pickup is constituted for emitting light beams such as laser beams by a laser diode, for focusing the light beams on the data recording face of the optical disc through an objective lens, for receiving a reflected light reflected from a data recording face of the optical disc and converting variation of intensity of the reflected light to electric signals by a photo-sensor and for outputting the electric signals. The optical pickup is moved in a radial direction of the optical disc.
An objective lens of the optical pickup is provided on a lens holder. The lens holder is movably borne not only in a direction perpendicular to the data recording face of the optical disc but also in a direction parallel to the data recording face of the optical disc and crossing substantially at right angle with data recording tracks on the data recording face of the optical disc.
A focusing coil and a tracking coil are provided on the lens holder further to the objective lens for moving the lens holder. The focusing coil minutely moves the objective lens on the lens holder in the direction perpendicular to the data recording face of the optical disc by electro-magnetic action with a magnet provided on a base member of the optical pickup. The tracking coil minutely moves the objective lens on the lens holder in the direction parallel to the data recording face of the optical disc, similarly to the focusing coil.
For reproducing the data from the optical disc, the objective lens of the optical pickup is moved in the direction perpendicular to the data recording face of the optical disc in a manner so that the concentration point of the focused light beam is just placed on the data recording face of the optical disc. Subsequently, the objective lens of the optical pickup is moved in the radial direction of the optical disc in a manner so that the concentration point of the focused light beam is just placed on the data recording track on the optical disc, while the concentration point of the focused light beam is placed on the data recording face of the optical disc.
Such the focusing and tracking operations of the optical pickup are executed by controlling current supplies to the focusing coil and the tracking coil corresponding to the electric signals outputted from the photo-sensor of the optical pickup. Pits formed on the data recording tracks on the optical disc are sensed from the electric signals outputted from the photo-sensor of the optical pickup, while the light beam is focused and tracked on the data recording track on the optical disc. Thus, the data are read out from the optical disc and will be reproduced.
For recording the data on the optical disc, pits corresponding to the data to be recorded are formed on the data recording tracks by concentrating the light beams pulsatively on the data recording track on the optical disc by the laser diode of the optical pickup.
In a conventional optical disc apparatus, which is, for example, shown in publication gazette of Japanese patent application 61-34735, flaw, dust, or the like on the data recording face of the optical disc is sensed for preventing occurrence of erroneous operation due to the flaw, dust or the like.
In another conventional optical disc apparatus, which is, for example, shown in publication gazette of Japanese patent application 62-52756, the decentering of the optical disc loaded on the optical disc apparatus is sensed, and the decentering of the optical disc is adjusted so as to increase the response characteristics of the tracking servo control.
In still another conventional optical disc apparatus, which is, for example, shown in publication gazette of Japanese patent application 2-218026, when the focusing servo operation of the light beam is missed, the optical pickup is once moved to depart a predetermined distance from the data recording face of the optical disc, and the objective lens is approached to the data recording face by driving the focusing actuator so as not to contact the objective lens with the optical disc even when the overdrive of the tilting servo operation occurs.
In the above-mentioned conventional optical discs, the lens holder cannot move smoothly due to sticking of the lens holder when dust is adhered in a gap between the lens holder and the sliding shaft. In such the case, the data are sometimes reproduced erroneously from the optical disc due to unsmooth movements of the focusing operation and the tracking operations.